Injured Syrian children react as they are treated at a makeshift hospital on June 28 following a reported car bomb explosion at a popular market in the rebel-held town of Douma, northeast of the capital Damascus. Photo: Getty Images

Jamal Maarouf was a construction worker before the Syrian Revolution. When protests began, he organized large demonstrations in the mountain villages near his hometown. He later took up arms to battle regime forces, and soon commanded a battalion of 7,000 fighters. This January, Maarouf led a coalition of moderate Syrian rebels that routed the extremist group Islamic State in Iraq and Syria, or ISIS, from his province.

Six months later, ISIS has gone on to seize Iraq’s second city of Mosul. Iraqi Army troops that were trained for years by US forces simply fled the battlefield, leaving ISIS in control of advanced military hardware and vast weapons stores. Now ISIS is consolidating its control west of Baghdad, and could soon threaten the Iraqi capital or the oil-rich areas further south.

President Obama recently dismissed as “fantasy” the idea that Syrian “farmers, dentists and folks who have never fought before” could defeat both Syria’s Assad regime and the extremists like ISIS. Yet Syrians like Jamal Maarouf, who never fought before the revolution, have a better record against ISIS than US-trained Iraqi forces.

You see, Syria’s revolutionary farmers and dentists have a secret weapon, one that has allowed them to fight both Assad and the extremists even without sufficient arms: motivation.

Before the January offensive against ISIS, ordinary residents across rebel areas held massive anti-ISIS protests, inspiring mainstream Syrian rebels to form new coalitions that took the fight to the extremists. These outgunned rebels succeeded where well-armed Iraqi troops failed because they’re fighting for a cause widely supported by the civilians behind them, and they’re fighting for their own land.

Had the Obama administration armed these rebels at their peak, instead of merely declaring repeatedly that Bashar al-Assad’s fall was inevitable, there would likely be no ISIS today. Two years ago, Syrian rebels were making gains against the regime by the day. ISIS didn’t exist, and Syrian al Qaeda affiliate Jabhat Nusra claimed at most 1,500 combatants.

But global al Qaeda supporters gave Nusra superior weapons and funding, a step Obama has yet to truly take on behalf of mainstream rebels. As a consequence, Nusra grew stronger, and was later surpassed by the even more radical ISIS.

Syrian rebels are fighting a true two-front war. As they threatened ISIS’ main headquarters in January, Assad launched a vicious campaign of air raids on them that virtually emptied the largest city in northern Syria of civilians. That assault saved ISIS.

Now, after the fall of Mosul, regime bombers have finally launched air raids on the ISIS headquarters — but air power alone can’t really threaten it. Assad’s move is just a public-relations ploy — an effort to get Washington to support the regime as the best hope of stopping ISIS.

More relevant are events in eastern Syria: The ISIS attack on Mosul was launched from eastern Syria, in particular from the banks of the Khabur River, which was in Syrian rebel hands as recently as three months ago.

Now ISIS has returned to Syria with the US-made weapons it looted from Mosul, and threatens the city of Deir Ezzor, the largest population center in eastern Syria and a longtime rebel stronghold. If ISIS takes Deir Ezzor, it could launch an ever more catastrophic assault on Baghdad or southern Iraq without fear of attacks from its rear. Deir Ezzor City is now under a de facto joint siege by ISIS forces in the north and Assad forces in the south.

ISIS is also gaining in other rebel areas. On June 20, a man named Slah al-Quseir al-Musa was killed defending the strategic town of Mohassan from ISIS.

A university student when the revolution began, al-Musa left his studies to become a top protest leader and then rebel commander in Deir Ezzor. He died alongside four senior commanders of the US-endorsed Free Syrian Army, after refusing ISIS’ surrender terms.

Many other rebel leaders across eastern Syria have made the same calculation: They would rather die than see ISIS in their hometowns. As many as 7,000 Syrians have been killed since January fighting against ISIS.

Though more outgunned than ever, these rebels rely on motivation — that secret weapon of Syrian farmers, dentists and students — to bring victory despite impossible odds. They shouldn’t have to.

President Obama recently announced a $500 million “train-and-equip” program for moderate Syrian rebels, and this is most welcome. But rebels might be long gone from eastern Syria before the program clears Congress. Commanders tell me that the weapons most needed are what the United States has already provided on a very limited basis, such as TOW missiles.

If the president is serious about stopping ISIS, let alone aiding moderate Syrian rebels, he should use his executive authority to get these weapons now to the farmers, dentists, and students of eastern Syria.

Mohammed Alaa Ghanem is senior political adviser for the Syrian American Council, a board member of the Coalition for a Democratic Syria and a fellow at the Syrian Center for Political and Strategic Studies.